An Update......
Okay, I decided some detective work was necessary to rule out certain questions about my reloads, so I took 20 rounds out of three separate ammo cans of what I'd loaded, broke them down, and determined that NONE of them were overloaded, the most powder I got out of a round was 5.1 grains, most were less than that. I used an inertial bullet puller, which lets some of the powder jump out around the collet when the bullet is released, but it's generally pretty negligible, assuming you stop whacking the "hammer" when the bullet is pulled out.
I also calibrated my Chargemaster's scale before I began, it's always been dead-on,and I have no reason to suspect a problem there. I have a lot of check-weights of different sizes, and they all weighed what they should.
The bullets I used are from a local commercial caster, and don't appear to be any harder than normal, I still have several boxes on hand and my hardness tester tells me they're all about the same.
Some of the pulled rounds had magnum primers, some had standard primers, just like the ones I fired.
I also had a lengthy conversation with Engineer1911 at his behest, and while we talked about a lot of things, most of it was about reloading. He brought up a point I hadn't considered, that of the powder being stored in a warehouse somewhere for a long time before the "Pistol Powder Shortage of 2013" hit. I bought the powder in question in October of 2013, didn't use it until about six months ago, and of the five pounds I bought (when there was nothing else to be found) I still have most of one left. Having no AA#2 on hand to compare it with, I can't say it looks more like AA#2 or AA#5, but I do recall that when I photographed all the AA powders I had on hand several years ago, the only way I could tell most apart was by looking at the label next to them when I took the photos. AA#7 and #9 have smaller grains, but #2 and #5 look the same to me.
I use a lot of brass that's been fired numerous times, but sorting the older brass from the newer stuff would be impossible, I use what I have until the primer pockets loosen up or it splits. So some of the brass might be work hardened, but when I encounter a load where the bullet requires more force than normal to seat (like with military brass) I set it aside and put it in a different lot, usually to be shot in a stouter gun like my 686 or the GP-100, just in case there's an issue I don't want my 38's to be subjected to.
I know magnum primers can make pressures spike, but this is the ONLY time it's been so noticeable, and not all the hot loads had magnum primers, so I have to think it's a powder issue.
An earlier poster mentioned that he thought I might have AA#2 that was mis-labeled as #5, and thus far, that seems like the only thing that makes sense. That, or a very hot batch of AA#5, maybe one that was stored in a hot warehouse that altered the burn rate somehow. All the canisters were sealed, but far be it from me to say it's not possible.
It seems a call to Western Powders would be in order, the lot number should tell us how old the powder actually is, I suspect it's more than a couple years old, regardless of how long ago I bought it.
If anyone has any thoughts on what I may be overlooking, feel free to chime in, I'm all ears. If it was a few rounds here and there I'd chalk it up to discrepancies in the brass, but it's ALL of them, and I'm a bit concerned. Having loaded at least a half-million rounds of pistol ammo without this kind of issue leaves me wondering what's going on here.
